flag carrier

plural flag carriers

1. A person carrying a standard or flag, usually at sporting events and parades, previously on the battlefield.

   Synonyms: flag-bearer, standard-bearer

2. governmentA strong supporter of a cause, or perhaps the strongest and most visible supporter of said cause.

   Bill was the flag carrier of the movement to improve inner city education.

   Synonyms: flag-bearer, standard-bearer

3. businessA transportation company, such as a shipping or airline company, that is registered in a given state.
4. aeronauticsA national airline (typically having the flag, or other national insignia, on the tail).

   I'll be interested to see how this service does. It will be basic with fares to match, so will be akin to a budget airline taking on a flag-carrier.

   2021 June 30, Philip Haigh, “Regional trains squeezed as ECML congestion heads north”, in RAIL, number 934, page 52

5. governmentAn aircraft carrier serving as a flagship.